THE FUTURE PROSPECTIVITY OF THE PERTH BASIN

The Perth Basin may have been regarded in the past as prospectively poor, but things are about to change! Seismic quality was generally poor, reservoirs often tight and source- rock maturity data limited. Abundant source rocks which tend to have a predominance of Type III kerogens have been identified and the basin has often been referred to as gas prone, the two largest discoveries having combined recoverable reserves greater than 444 billion cubic feet (12.5 Gm3). Advances in seismic acquisition and processing, available from the early 1980s, is drawing back the veil that has enveloped major areas of the basin for many years. An estimated 29 wells out of 40 exploration wells studied in the northern area of the Perth Basin were drilled off- structure. Established plays are now being correctly delineated and oil- prone source rocks with good generative potential have been identified. Perhaps the most significant occurrence in the Perth Basin was the discovery of a new play in 1987 which stimulated a new round of activity. This will undoubtedly provide economic discoveries for the participants. This renewed prospectivity will spill over into the offshore areas in the near future. The northern area of the Perth Basin has an historic exploration risk of 12.5 per cent. With future exploration risk predicted at 20- 30 per cent, this area will become one of the most prospective onshore basins in Australia.